Moving this closer to the working state.

* Added extension method to FrameFormat to obtain the frame element
size.
* Removed redundant param in StreamOutputBase and StreamOutputSimple
ctor.
* If there is not enough data in the buffer for OutputDevice, the rest
will be zeroed.
Minor fix.

* In PortAudioOutputDevice, copied frames are now consumed.
Basic implementation of WMME I/O (only output).